1. Field of the Invention
The present invention relates to a method for dry-preserving a tissue of a multicellular organism at ordinary temperatures.
2. Background Art
The preservation of unicellular organisms can be easily conducted by various methods, but it is common that the preservation of the tissues (organs, meat, fresh vegetables, etc.) of multicellular organisms be conducted under refrigerated or frozen conditions. However, cryopreservation and cryotranport require a huge energy input and refrigerants, which are considered to cause environmental pollution.
Dr. Levine's group at the Center for Molecular Genetics, UCSD School of Medicine, California, USA, introduced and expressed trehalose synthetase derived from E. coli into the muscle fiber cells of humans, resulting in remarkable improvement of the dry resistance of the cells. In other words, after drying the cells for 24 hours, the water content of the cells was measured at almost zero. At that time, the cells were submerged in water. The control cells had all died but 25 to 60% of the cells that expressed trehalose therein indicated life activities (Technical Literature 1).
However, when the drying is conducted for a period exceeding 3 days, the cells exhibited a remarkably low survival rate. This indicates merely that the deactivation of enzyme activity was delayed for a short period by trehalose in dried tissues in a lethal process. When the water content of cells becomes zero, metabolic activities theoretically stop. If the cells have potential recovability at that time, the survival rate should be maintained at a certain level regardless of the time length after drying.
Their results clearly indicate that the accumulation of trehalose is a necessary condition but not a sufficient condition for dry resistance of cells. Their system still has many problems to be solved.
(Technical Literature 1)                Ning Guo et al. (2000) Trehalose expression confers desiccation tolerance on human cells. Nature Biotechnology (18) pp. 168-171        
(Technical Literature 2)                Hinton H. E. (1951) A new chironomid from Africa, the larva of which can be dehydrated without injury. Proc. Zool. Soc. Lond. 121, pp. 371-380        
(Technical Literature 3)                Denlinger D. L. (1985) Hormonal control of diapause. In Comparative Insect Physiology, Biochemistry and Pharmacology (ed. G. A. Kerkut and L. Gilbert), pp. 354-412. Oxford: Pargamon Press.        